Summary: Chronic infection with hepatitis B virus (HBV) is a major cause of chronic liver disease, cirrhosis and hepatocellular carcinoma (HCC) worldwide. Globally there are an estimated 400 million persons infected with HBV. In the United States, there are 1.25 million affected individuals and the epidemiology of the infection is changing due to immigration of persons from endemic regions. The natural history of chronic hepatitis B (CHB) also appears to be changing with an increasing prevalence of HBeAg negative chronic hepatitis B. Knowledge of the rate of progression between individuals with HBeAg positive and negative CHB is unknown. An equally important and related issue is the clinical assessment of disease severity in patients with CHB. Unfortunately, there are no good laboratory markers of disease severity. Liver biopsy is the accepted gold standard for assessing disease severity and cirrhosis but is costly, invasive, and associated with complications, which often limits patient acceptability as well as being subject to sampling error ranging from 15% to 25%. Non-invasive methods to assess disease severity are highly desirable for physicians caring for patients with CHB. Despite the availability of safe and effective oral nucleoside analogues for treatment of CHB, therapy remains problematic due to the need for prolonged therapy and limited effectiveness of alternate treatment -interferon. Identifying the optimal regimen, defining when to treat, for how long and when to stop therapy are major unresolved issues. In addition, defining the best parameters to monitor patients both on and off therapy are not clear. Hypotheses/problems addressed: 1) Define the host, viral and environmental factors that determine the natural history and outcome of HBV infection. To study this problem, we have analyzed a large database of untreated and treated patients with CHB (n750), focusing on the outcome of infection after hepatitis B e antigen (HBeAg) seroconversion. We analyzed factors that predict progression to HBeAg negative chronic hepatitis B as well as factors that predict HBsAg loss. The database is being used to develop a non-invasive model to predict fibrosis progression in patients with CHB. We also plan to evaluate the role of transient ultrasound elastography (Fibroscan) to assess fibrosis stage in persons with CHB. These results will be compared to liver biopsy and a series of non-invasive serum fibrosis markers. The goal is to develop a series of blood and imaging tests that will obviate the need for liver biopsy in most patients with CHB. Reactivation of chronic hepatitis B is a troublesome concern of previous recovered patients who receive intensive chemotherapy. Factors associated with reactivation are not well understood. In collaboration with colleagues at NHLBI, we have studied two cohorts of subjects with a variety of underlying medical conditions requiring either myeloablative or non-myeloablative bone marrow transplants to better understand the factors associated with reactivation of chronic hepatitis B. We are also focusing on whether the presence or absence of antibody to hepatitis B surface antigen (anti-HBs) is important for reactivation. The Liver Diseases Branch is participating in a large multicenter study, the Hepatitis B Research Network, to define the natural history of HBeAg positive and negative chronic hepatitis B. This study has enrolled >1800 patients at 13 North American sites. Primary questions that will be spearheaded by our group will be to identify the predictors of spontaneous HBeAg loss in immunetolerant patients and to evaluate the natural history of patients with elevated HBV DNA levels but normal ALT who are also HBeAg negative-so called indeterminate phenotype. 2) Develop and evaluate novel, safer and more effective therapies for chronic viral hepatitis. Current therapy of CHB remains less than optimal. Relapse is common if treatment is discontinued after one year in the absence of HBsAg loss. Consequently, nucleos(t)ides must often be administered long-term or indefinitely. However, long-term use is associated with the development of antiviral resistance with resulting loss of clinical benefit and increased risk of side effects. Therefore, an important challenge in HBV management is how to use these agents most effectively to achieve a long-term response while avoiding the issue of antiviral resistance. We are taking multiple approaches to this problem. The first is to compare the combination of tenofovir and emtricitabine compared to tenofovir for patients with CHB. Tenofovir is a nucleotide analogue that is more effective than adefovir at suppressing HBV DNA and has an excellent resistance profile. This study will examine the long-term efficacy and safety of tenofovir and emtricitabine versus tenofovir alone in patients with HBeAg positive and negative CHB with the goals of maintaining long-term viral suppression ands preventing the emergence of viral resistance. To date 33 patients have been enrolled and started on therapy. Long-term results are pending. The second approach is to combine peginterferon alfa with tenofovir compared to tenofovir alone. This is being conducted under the auspices of the hepatitis B research network and is a multicenter trial that will enroll 375 subjects. The third approach is to discontinue therapy in patients receiving long-term nucleos(t)ide analogues. To address this question we have initiated a prospective trial to withdraw patients from medication and observe for benefits (HBsAg loss) or adverse events (ALT flares, HBeAg seroreversion and fulminant hepatitis). To date 15 patients have been withdrawn from therapy. 3) Elucidate the viral pathogenesis of HBV infection and mechanisms of anti-viral resistance The course of CHB following the development of anti-viral resistance is highly variable with some patients showing continued viral suppression, some with an accelerated course and others who lie in-between. We hypothesized that following initial viral breakthrough, compensatory mutations that affect viral replication may account for the different clinical presentations observed. We are also investigating whether the outcome of resistance is affected by the presence of naturally occurring mutations- the pre-core and the double core promoter mutations, in HBeAg negative patients. We are investigating the role of pre-core and basic core promoter mutations on the natural fluctuations in HBV DNA levels observed during the natural course of HBeAg negative chronic hepatitis B. We hypothesize that elevation in HBV DNA levels are due to an increase in variant virus over wild type virus. To achieve this we are quantifying the amounts of pre-core and basic core promoter mutations relative to wild type virus at different time points when virus levels are fluctuating -both high and low. Finally, we are exploring potential mechanisms for clearance of HBsAg-the viral protein associated with clearance of HBV-by measuring the kinetics of HBsAg loss using a quantitative HBsAg assay.